Superman's Pal Jimmy Olsen#17(1956)

Superman takes Jimmy up in a discarded rocket that Superman repaired, while taking Jimmy up into space, Superman has to smash a meteor. In doing so, he has to let go of Jimmy's rocket, and the ship traveling so fast breaches the time barrier. Jimmy parachutes from the rocket once he reaches a safe altitude and soon learns that he's traveled forward in time to the 50th Century. Visiting the Daily Planet of the future Jimmy falls down an elevator shaft and is almost injured but is saved by a robotic bird. When people notice him and comment on his strange attire, he explains who he is. To his surprise, the people of the 50th Century believe that Jimmy Olsen was the legendary Superman. He soon shown newspaper headlines that were saved from the 20th Century that talk about Jimmy Olsen pulling of super-feats, realizing that these were all reports from events where Superman did tricks to make Jimmy appear to have super powers. He is unable to convince people because there are no existing photographs of Superman that have endured the ages. Given Superman's cape, Jimmy hears of an ocean liner that is in peril, Jimmy tries to explain that he has no super-powers. However, this is when a professor Xerxes steps in. Explaining that there is a Kryptonite meteor passing the Earth, he gives Jimmy devices that mimic all of Superman's super-powers and send him off to rescue the ocean liner. Jimmy soon learns that a man named Jon Smyth has published a book claiming that Superman is a hoax, and exposes that Jimmy was using special devices to save the day. Jimmy decides it's time to call in the real Superman, who is able to hear his signal watch back in the 20th Century. Superman arrives in the 50th Century and proves to the people of the future that Superman truly exists. Superman also unmasks Jon Smyth as Professor Xerxes, who hope to exploit Jimmy to sell more copies of his book. With Jimmy's goal accomplished the two return back to the 20th Century. However, upon returning to the present, all Jimmy's memories of the future are wiped from his mind, a side effect for humans who travel through the time barrier.